On this type of apparatus, for example, the power transmission unit and the power reception unit are magnetically coupled by magnetic resonance, electromagnetic induction, or the like. This provides power transfer in the wireless manner between the power transmission unit and the power reception unit. On this type of apparatus, a leakage electromagnetic field is reduced between the power transmission unit and the power reception unit.
For example, Patent document 1 discloses an apparatus configured to monitor current flowing through each of a primary (power transmission side) coil and a secondary (power reception side) coil, and to adjust frequency and a resonance capacitor such that the primary coil and the secondary coil resonate in a state in which the current flowing through the primary coil is opposite to the current flowing through the secondary coil.
Alternatively, Patent document 2 discloses the following technology; namely, if a power transmitting coil is to some extent close to a power receiving coil, then, two drive frequencies with peak transmitted energy appear, in the magnetic resonance between the power transmitting coil and the power receiving coil, and thus, the drive frequency on a high frequency side is used for the drive to set a current phase difference between the power transmission and reception in anti-phase, thereby relatively weakening a generated magnetic field.